Fuse-plug



R. S. PORTER.

FUSE PLUG.

APPLICATION FILED APR. l6. I919.-

Patented May 11, 1920.

flaertSParteg' WITNESSES ATTORNEY UNITED STATES PATENT OFFICE.

ROBERT S. PORTER, OF SAN DIEGO, CALIFORNIA, ASSIGNOR OF ONE-HALF TO DONALD C BURNHAM, OF SAN DIEGO, CALIFORNIA.

FUSE-PLUG.

Specification of Letters Patent.

Patented May 11, 1920.

Application filed April 16, 1919; Serial No. 290,399.

To all whom it may concern Be it known that I, ROBERT S. PORTER, a citizen of the United States, residing at San Diego, in the county of San Diego and State of California, have invented a new and useful FusePlug, of which the following is a specification.

This invention has reference to fuse plugs for electric circuits, and its object is to provide a plug wherein the blown condition of the plug is made clearly visible and the fusible element of the plug is readily renewable parent plate forming a top or cover for the interior chamber of the body member. The indicating portion of the elastic member is retained in a practically invisible or nonindicating position by a piece of fusible metal, such as usually employed in fuse plugs, and which may be applied to the plug or renewed, when ruptured, with great ease and without necessitating the disturbance of the cover of the fuse plug, which cover, if removed, might easily be left off when the 'plug is recharged, with the then ever present danger from shock on contact or the throwing of molten metal in case of a blow-out.

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawing forming part of this specification, with the understanding, however, that the invention is not confined to any strict conformity with the showing of the drawing, but may be changed and modified so long'as such changes and modifications mark no material departure from the salient features of the invention as expressed in the appended claims. I

. In the drawing Figure 1 is a longitudinal. diametric sec-" tion, with some parts in elevation, of a fuse plug embodying the invention and ready for Fig. 2 is a view similar to Fig. 1 but showing the positionof the parts when the fusible metal is blown.

Fig. 3 is a view similar to Fig. 2 but showing a somewhat modified form of the invention.

Fig. 4 is a plan view of a gripping terminal for the fusible material.

Fig. 5 is an elevation of a form of fusible element which may be used in connection with the plug of Fig. 1.

Fig. 6 is a perspective view of an indicating device for use in connection with the plug of Fig. 3.

Fig. 7 is a perspective view of a fusible member for use in connection with the structure of Fig. 3 and associated figures.

In the drawing, there is shown in Fig. 1 and associated figures a fuse plug body 1, which, in accordance with the usual custom, may be made of earthenware of the character commonly known as porcelain in the fuse plug art. The body member 1 has an exteriorly threaded portion 2 to which is applied an exterior sleeve 3 conforming to the threaded portion so that the plug as a whole may be screwed into a suitable socket,.the.sleeve 3 being of metal to serve as a conductor. The bgdy member 1 has a chamber 1 in it, open at one end and there closed by a sheet 5 customarily formed of mica so that the interior of the chamber 4 is usually visible. Sometimes the mica employed is of a more or less cloudy nature, wherefore the contents of the chamber are either invisible at a short distance beyond the mica sheet or so poorly .visible as to make it difficult to determine,

in good condition or has been blown. It IS the custom to hold the mica sheet 5 to the corresponding end of the body of the plug by a ring 6 having edge portions 7 turned or spun over a laterally expanded bead 8 about the periphery of the body member, the mica covering 5 being thereby rendered practicglly permanent in its connection with the p ug.

The other end 9 of the body member, that is, that end remote from the mica covering- 5, is customarily tapered so that it may be arranged to constitute or supporta central terminal for the plug.

In accordance with the invention, the tapered end9 has a tapered passage 10 therethrough with the small end opening into the eeose chamber 4.. l itted to the tapered passage 10 is a taper block or plug 11 having at one end a plate-like expanded head 12 which may correspond more or less closely to the small extremity of the tapered end 9. Through the plug 11 and the head or plate 12, from one side of the plug through the diametrically opposite side thereof and continued through the plate 12 on the same side to the outer margin thereof, is a slot 13 so that the plug, as a whole, is more or less yielding or elastic. Centrally through the plug the slot 13 is enlarged, as shown at 14c.

Within the chamber 4 there is located a coiled spring 15 which may be, although is not necessarily, of spiral form, and is so made that when permitted to expand it will extend from the base end of the plug to the mica cover plate 5. Que end of this spring, say at the larger end thereof, is provided with a lateral extension 16 which is threaded through an opening 17 through the side of the body member close to the basic end thereof and outside of the body member is soldered or otherwise made fast to the sleeve 3, as indicated at 18, so as to be electrically connected therewith at all times.

The end of the spring 15 remote from the plug 11 is provided with a disk 19 fast there to, or otherwise arranged, so as to bear against'the inner face of the transparent cover plate 5 when permitted to do so. The disk 19 may have the surface directed toward the cover plate 5 rendered particularly visible by paint or otherwise, whereby when the disk or expanded portion of the spring 15 is against the inner face of the sheet or plate 5 it may be sufficiently obtrusive to attract attention.

The inner face of the disk 19 is provided with a hook 20 which mayconstitute a continuation of the spring 15 or may be otherwise formed or replaced b any suitable holding means for one ternnnal portion of a fuse member 21. The fuse member is usually in the form of a wire or strip of fusible metal formed at one end with aneye 22 for engagement with the hook 2'0 and this strip of fusible metal is long eno h to engage the hook and pass through t e opening 14 in the plug or block 11 and extend beyond the latter when the spring 15 is in the expanded condition.

When the plug is to be loaded or after. the plug has been blown the block 11 is removed from the opening 10, the fuse wire 21 is inserted through the opening 10 and through the spring 15 and applied to the hook 20. Then the-end of the wire 21 outside of the plug body is threaded through the opening 14 and the block 11 is moved into the opening 10. After this is done the fuse wire is pulled sufficiently to partially compress the spring 15 and that end of the fuse wire outside of the plug is held until the block 11 is forced into the passage 10 to a degree clamping the wire and also holding the block in place, the taper formation of the block and the passage 10 causing the approach of the split portion of the block into tightly clamping relation to the wire, which latter may then be bent over and cut off or otherwise secured in the block, or dependence may be had upon the frictional engagement of the block with the wire. Under such conditions the indicator 19 is drawn far enough into the chamber 4; to partly hide it, or, in the case of smoky mica being present, the indicator may be wholly invisible or dimly visible only with difficulty.

With such a fuse plug even a casual observation will show that the plug is in working condition because the indicator is not seen in contact with the cover 5, whereby it is evident that the fuse wire is intact. Should a blow-out occur the continuity of the wire is broken and the expansion of the spring at once carries the disk 19 into contact with the inner face of the mica sheet or plate 5, thus showing to the observer in a prominent or clearly visible manner that the wire is no longer intact and the fuse is inoperative. This is a valuable feature where fuses are used in pairs or in greater number in the several branches of a multi-line system, thereby avoiding the necessity of trying out the fuses to determine which fuse has been rendered useless.

The defective or blown fuse is removed from its socket and the block 11 is also removed from the body of the fuse, thus giv ing access to the chamber 4 and permitting the removal of the burned out wire and any particles of fusible metal which may have found lodgment in the chamber 1.

A new fuse wire is then inserted into the chamber 1, through the expanded spring 15, and the eye end 22 of the wire is engaged with the hook 20, whereupon the procedure already described of resetting the fuse plug is followed.

The taper plug 11 is long enough so that when forced into the opening 10 to an extent causing it to clamp the fuse wire, the head is slightly distant from the basic end of the body member, thus making the clamping particularly secure and causing the taper plug to bind firmly in the tapering opening 10.

In Fig. there is shown a somewhat modified form of the structure, differing from that of Fig. 1 and associated figures in the construction of the fuse strip or wire and the elastic indicating terminal engaged by the wire. The indicating terminal is in the form of 'a spring strip 23 long enough to be passed through an opening 24: in the side of the body member 1 at the end of the screw sleeve 3 remote from the basic end of the plug and the strip is soldered or otherwise secured to the sleeve 3, as shown at 25. That end of the strip 23 remote from the end secured to the sleeve 3 is expanded into a disk or other suitably shaped indicating member 19*, which, when the strip is located within the chamber 4 and is unrestrained, bears against or is located very close to the inner faceof the plate 5. Formed in the strip 23 is a perforation 26 provided with a narrow side entering neck 27 sufficient to pass the body portion of a fuse'wire or strip 21 having an expanded head 22 which will seat and lock in the perforation 26. When the parts are adjusted for operation the head 22 cannot spontaneously escape from its seat in the perforation 26 and on drawing the wire out through the opening 10 and then apply-.

ing 'the'block 11 the wire may be fastened, as in the structure shown in Fig. 1. This will bend the strip 23 to a sufiicient extent to move the indicator 19 into the chamber 4 to a distance making it evident that the fuse Wire is intact.

It is to be understood that it is not necessary that the indicator 19 or 19 be in actual contact with the inner face of the plate 5 for it may be somewhat spaced therefrom and still indicate that the wire has been ruptured.

What is claimed is 1. A fuse plug comprising a body member with an interior chamber, a permanent transparent cover for the chamber, a removable conducting block for the end of the body member remote from the cover, and

an elastic conducting device with an indicating plate of relatively large area carried thereby and having a normal tendency to move the plate toward the transparent cover, the elastic conducting device having means for the attachment thereto of a fusible device and the block being shaped to pass and grip the fusible device, whereby to normally hold the elastic member in a constrained position and release said elastic member to move the indicating part thereof toward the cover member on the rupture of the fusible-device.

,2. A fuse plug having a chamber therein, a transparent cover, an elastic conducting member within the chamber having a normal tendency toward the cover and provided witha laterally extended indicating meansat'all times within the chamber and movable with the elastic member into juxtaposition to the inner face of the cover, and means for the attachment of a fusible device to the elastic member in position to hold the latter against the normal tendency of said elastic member with the indicating means distant from the cover.

3 A fuse plug having an interior chamher with a transparent cover member, a spring device at all times wholly within the chamber and carrying laterally extended indicating means movable by the spring device into juxtaposition to the transparent cover, and holding means for a fusible element whereby the fusible element may be connected at one end to the elastic means and at the other end to the holding device to move the indicating means away from the transparent cover and there hold it against the normal tendency of the elastic means while the fusible element is intact.

4. A fuse plug comprising a body member with a transparent cover at one end and having a taper passage at the other end, an elastic conducting means located at all times wholly within the chamber and having laterally extended indicating means thereon movable by the normal tendency of the elastic means into substantially parallel juxtaposition to the cover, said elastic means having means for the ready attachment thereto of one end of a fusible element, and a taper block adapted to the taper passage in the body member, said block having a single slotted portion to pass the fusible element and permit the block to compress upon the fusible element when said block is inserted in the taper passage, whereby the fusible and a transparent plate constituting a cover for the chamber with the body member having a taper passage through it at the end of the chamber remote from the cover member, a one-piece split taper block insertible into and removable from the taper passage, and an elastic conducting member within the chamber and provided with expanded indicating means movable into juxtaposition to the inner face of the cover member under the normal tendency of the elastic conducting member, whereby a fusible element may be connected at one end to the elastic member'to be clamped at the other end by the taper block to hold the elastic member under tension until the fusible member is ruptured.

6. A fuse block comprising an insulating body member with exterior conducting means and provided 'with an interior chamber having a .taper passage leading therefrom through the basic portion of the block, a transparent plate constituting a closure for the other end of the chamber, a taper plug split at one side and adapted to the taper passage and constituting the center terminal of the plug, an elastic conducting member at all times within the chamber and connected to the exterior conducting portion of the plug other than the center terminal and provided with an indicator movable into juxtaposition to the inner face of the transparent cover under the normal tendency of the elastic conduct- 5 ing member, and a fusible element having means for connecting it to the elastic conducting member Within the chamber and engageable by the split block, whereby the fusible member is utilized to hold the elas- 10 tic conducting member in opposition to its normal constraint to locate the indicating means in distant relation to the cover member.

In testimony that I claim the foregoing as my own I have hereto aflixed my signature. '15

ROBERT S. PORTER.

i'vitnesses JOHN BURNHAM, A. A, MURPHY. 

